Genetics

1. Crime and Genetics

It is a common misconception that the link between biology and crime is primarily genetic, as there is much more to biology than the study of genes. Our genes do have a profound influence on us, so a great deal of research has been conducted on the genetics of behavior. As behavior is highly complex, in almost all cases, any behavioral trait will be influenced by a large number of genes, not just two or three.

Therefore, a gene for “crime” or for any complex behavior cannot exist. Most behavior is governed by thousands of genes, with each contributing a small amount toward a person exhibiting that behavior.

These genes are not criminogenic or capable of producing criminals on their own but could lead to a person offending under particular circumstances.

EXAMPLE

Impulsivity is a behavior that could potentially lead to a criminal event, such as not considering the consequences of stealing a car for a joyride. Of course, impulsivity could equally result in buying way too many shoes, which is not a criminal behavior.

How such a behavior is enacted is greatly influenced by many other factors, including socioeconomic status (SES), education, and peers.

term to know

Criminogenic

A production of or a tendency to produce crime or criminals.

1a. Heritability Studies

A great deal of genetic and environmental research has been conducted using twin and adoption studies. These studies compare the impacts of genes and the environment on behavior.

Twins are an ideal study group, as there are two types of twins:

• Monozygotic (MZ) or “identical” twins begin as a single zygote (one egg and one sperm) that, very shortly after fertilization, divides into two, resulting in two genetically identical babies, aside from small early mutations that may occur (Jonsson et al., 2021).
• Dizygotic (DZ) twins result from two zygotes and only share 50% of their genes. (Actually, we share 99% of our DNA with every other human being, but of the 1% that is different between all people, siblings share 50%.) DZ twins, in general, share 100% of their environment and 50% of their genes, whereas MZ twins, in general, share 100% of both their environment and genes.

did you know

One problem with twin studies is the assumption that each set of twins shares the same environment, but MZ twins, who look identical, may share more of their environment than DZ twins, who look less similar and may be of different sexes. Such factors would impact the results (Burt & Simons, 2014).

Adoption studies offer a much more powerful method of separating the effects of genes and the environment by comparing adopted children with their adopted and biological families. In such situations, biological parents can only contribute biological effects, and adoptive parents can only contribute environmental effects on the behavior of adopted children, as the studies focus on children adopted by nonrelatives, neatly separating biological and environmental effects.

EXAMPLE

Many large studies conducted worldwide have shown that a child is much more likely to offend if their biological rather than adoptive parents were offenders, and even more likely if both are offenders (Mednick et al., 1987).

These findings show both a heritable relationship and the impact of the environment.

1b. Gene–Environment Interactions (G x E)

People with different genetic backgrounds may react differently to the same environment. We know that many risk factors influence the likelihood of committing a crime, such as the following:

• Child abuse
• Low socioeconomic status (SES)
• Peer pressure

EXAMPLE

Someone without a predisposition for criminal behavior may never offend, regardless of an adverse environment, and a person with a predisposition for criminal behavior may never offend if they do not experience adversity.

Adversity may be any form of hardship, which includes trauma; physical, sexual, or emotional abuse; starvation; or any form of severe suffering.

did you know

Males with a certain form of a gene for a neurotransmitter or chemical messenger have a higher predisposition for aggressive behavior only if they are severely physically abused as a child. If they are not abused or never exposed to this trigger, they are no more likely to be aggressive than any other male (Caspi et al., 2002).

A predisposition, together with an adverse environment, increases risk but still does not guarantee a criminal outcome, because there are so many combinations that could occur related to predispositions and environment (Gajos et al., 2016). Several models predict these variations, such as the diathesis–stress model, which suggests that a genotype has a number of different alleles, or different gene variants, and each adds a tiny bit of risk (Bersted & DiLalla, 2016). So, this model predicts that the basic causes of antisocial behavior are triggers in the environment interacting with the person’s genotype (Boardman et al., 2014).

EXAMPLE

Children with certain risk factors are at greater risk of antisocial behavior if they experience parental conflict (Feinberg et al., 2007). Additionally, if they are exposed to a bad environment, they are very likely to be antisocial, but if they are exposed to a good environment, they may not show any antisocial behavior at all.

These findings help identify not only environmental triggers but also protective factors that can enhance or even eliminate risk.

terms to know

Adversity

A state or instance of serious or continued difficulty or misfortune.

Neurotransmitter

A chemical that allows neurons to communicate with each other throughout the body.

Diathesis–Stress Model

A psychological theory, also known as the vulnerability–stress model, which attempts to explain a disorder or its trajectory as the result of an interaction between a predispositional vulnerability, the diathesis, and stress caused by life experiences.

Allele

One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

1c. Epigenetics

Epigenetics, like criminology, studies how your behaviors and environment can cause changes that affect the way your genes work. Unlike genetic changes, epigenetic changes are reversible and do not change your DNA sequence, but they can change how your body reads a DNA sequence.

Interestingly, although only the expression of the genes changes and not the DNA sequence, these epigenetic changes can be passed on to the next generation, so they are heritable (National Human Genome Research Institute, 2020). This exciting new area of study is only just being explored, primarily as it relates to health care, but some work has been done on criminogenic behavior that helps explain G x E interactions. The epigenome is changed by the environment to allow the body to respond; changes may occur in neural development or in neurotransmitter or hormonal function, which could impact behavior.

did you know

A study on rodents showed that maternal care could result in gene expression changes in the first week of life, with increased maternal care resulting in calmer offspring that exhibit less stress in new environments than those with low maternal care (Weaver et al., 2004). Another study showed that when rat pups were abused for 30 min a day during their first week of life, the brain changes lasted a lifetime, resulting in rats that abused their own offspring (Roth & Sweatt, 2011). In both studies, the changes could be reversed with medication.

Many studies on children have demonstrated that early life adversity and parenting decisions have an epigenetic effect on a child’s developing brain that can impact their future behavior, mental abilities, reaction to stress, and resilience to further adversity, making them less able to cope. Such changes can be transgenerational, or passed on to later generations. This is a relatively new understanding and means that the experiences of your parents can epigenetically affect their DNA, which will impact the way your genes and even your children’s genes will be expressed.

Studies, like the one by DeLisi & Vaughn (2015), show that this epigenetic effect can do the following:

• Increase antisocial behavior and aggression
• Reduce empathy
• Increase depression
• Reduce normal stress responses, resulting in a lack of fear of danger or consequences

• Antisocial behavior
• An inability to deal with stressors
• A lack of parenting skills

terms to know

Epigenetics

The study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself.

Transgenerational

The characteristic of genetic information passed on from one generation to the next without direct genetic inheritance.

1d. Social Implications

When considering any heritable factor that impacts a physical characteristic with social implications, it must be separated from the social effect.

When certain heritable characteristics such as skin color or ancestry put a person at a social disadvantage—for instance, by making them more likely to experience poverty, a lack of education, starvation, or abuse—their lack of success or increased risk is blamed on the inherited factor. In reality, this is a social construct and a result of systemic discrimination.

Possessing that heritable characteristic greatly reduces that person’s chances of success in that particular society, and it is purely the environmental disadvantages that cause the outcome, not genetics or physical differences themselves.

did you know

This discrimination, rather than ancestry, in part explains the disproportionate number of African Americans incarcerated in the United States.

REFERENCES

Anderson, G. S. (2020). Evidence for genetic predispositions for criminogenic behavior: Twin and adoption studies. In Biological influences on criminal behavior (2nd ed., pp. 83–110). Taylor & Francis Group.

Bersted, K. A., & DiLalla, L. F. (2016). The influence of DRD4 genotype and perinatal complications on preschoolers’ negative emotionality. Journal of Applied Developmental Psychology, 42, 71–79. doi.org/10.1016/j.appdev.2015.12.001

Boardman, J. D., Menard, S., Roettger, M. E., Knight, K. E., Boutwell, B. B., & Smolen, A. (2014). Genes in the dopaminergic system and delinquent behaviors across the life course: The role of social controls and risks. Criminal Justice and Behavior, 41(6), 713–731. doi.org/10.1177/0093854813514227

Burt, C. H., & Simons, R. L. (2014). Pulling back the curtain on heritability studies: Biosocial criminology in the postgenomic era. Criminology, 52(2), 223–262. doi.org/10.1111/1745-9125.12036

Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., Taylor, A., & Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854. doi.org/10.1126/science.1072290

DeLisi, M., & Vaughn, M. G. (2015). The vindication of Lamarck? Epigenetics at the intersection of law and mental health. Behavioral Sciences & the Law, 33(5), 607–628. doi.org/10.1002/bsl.2206

Feinberg, M. E., Button, T. M. M., Neiderhiser, J. M., Reiss, D., & Hetherington, E. M. (2007). Parenting and adolescent antisocial behavior and depression: Evidence of genotype x parenting environment interaction. Archives of General Psychiatry, 64(4), 457–465. doi.org/10.1001/archpsyc.64.4.457

Gajos, J. M., Fagan, A. A., & Beaver, K. M. (2016). Use of genetically informed evidence-based prevention science to understand and prevent crime and related behavioral disorders. Criminology & Public Policy, 15(3), 683–701. doi.org/10.1111/1745-9133.12214

Jonsson, H., Magnusdottir, E., Eggertsson, H. P., Stefansson, O. A., Arnadottir, G. A., Eiriksson, O., Zink, F., Helgason, E. A., Jonsdottir, I., Gylfason, A., Jonasdottir, A., Jonasdottir, A., Beyter, D., Steingrimsdottir, T., Norddahl, G. L., Magnusson, O. T., Masson, G., Halldorsson, B. V., Thorsteinsdottir, U., Helgason, A., . . . Stefansson, K. (2021). Differences between germline genomes of monozygotic twins. Nature Genetics, 53, 27–34. doi.org/10.1038/s41588-020-00755-1

Mednick, S. A., Gabrielli, W. F. J., & Hutchings, B. (1987). Genetic factors in the etiology of criminal behavior. In S. A. Mednick, T. E. Moffitt, & S. A. Stack (Eds.), The causes of crime: New biological approaches (pp. 74–91). Cambridge University Press.

Mullineaux, P. Y., & DiLalla, L. F. (2015). Genetic influences on peer and family relationships across adolescent development: Introduction to the special issue. Journal of Youth and Adolescence, 44, 1347–1359. doi.org/10.1007/s10964-015-0306-0

National Human Genome Research Institute. (2020, August 16). Epigenomics fact sheet. U.S. Department of Health and Human Services, National Institutes of Health. www.genome.gov/27532724/epigenomics-fact-sheet/

Roth, T. L., & Sweatt, J. D. (2011). Annual research review: Epigenetic mechanisms and environmental shaping of the brain during sensitive periods of development. The Journal of Child Psychology and Psychiatry, 52(4), 398–408. doi.org/10.1111/j.1469-7610.2010.02282.x

Weaver, I. C. G., Cervoni, N., Champagne, F. A., D’Alessio, A. C., Sharma, S., Seckl, J. R., Dymov, S., Szyf, M., & Meaney, M. J. (2004). Epigenetic programming by maternal behavior. Nature Neuroscience, 7, 847–854. doi.org/10.1038/nn1276